The present invention generally relates to test tube holding apparatus and, more specifically, to a test tube rack assembly suitable for mounting a plurality test tubes during scientific procedures.
During scientific experimentation, such as biological testing procedures, it is often necessary to utilize a number of test tubes holding liquid culture specimens. The test tubes are generally held in racks while the culture specimens are grown. These racks may also be attached to shaking or stirring devices, such as orbital shaker tables, to mix the contents of the test tubes and enhance the culture growth activity. The test tubes may also be incubated, refrigerated and subjected to different lighting conditions during such experiments or culturing procedures.
As cultures are grown in test tubes, it is generally advantageous to maximize direct contact of the culture medium with air. Shaking the test tubes is one way to increase the exposure of culture medium to air at the top of the test tube. In this regard, shaking the culture medium creates a larger undulating surface area in the medium. Shaking also ensures that a greater volume of culture medium is brought to the surface to directly react with air at the top of the test tube.
Another manner of increasing the surface contact area of the culture medium with air for reaction purposes is to angle the test tubes from vertical such that the upper surface of the medium takes on a larger, oval shape. Various make-shift ways of accomplishing this have been used by scientists and other laboratory personnel. These have included leaning individual test tubes or the rack in which they are held against other structure at an angle and using tape to secure the test tubes against the structure as they are being stirred or shaken.
Certain test tube racks or holders have been proposed for orienting test tubes at an angle to increase the rate of culture growth by increasing surface area exposure of the culture. In this regard, U.S. Pat. No. 4,932,533 discloses a test tube transportation container having an insert for holding the test tubes and culture medium contained therein at a predetermined, fixed angle. This holder does not allow adjustment of the angle and, as it is designed for transportation or shipping purposes, the holder is not particularly well suited for laboratory use.
An adjustable test tube carrier is disclosed in U.S. Pat. No. 4,770,381. In this patent, one embodiment of the carrier is angularly adjustable by way of a curved slot which carries a threaded stud secured by a wing nut. The adjustment feature and other aspects of this holder suffer from certain disadvantages. For example, while the test tube carrier has two extreme angular positions defined at the ends of the curved slot, it does not provide the ability to repeatedly set the carrier at a plurality of discrete angular positions between these extremes. The lack of assurance that test tubes in different experiments or tests are being held at the same angle could lead to misleading results in some cases. Also, it may be awkward for one operator to angle the test tube carrier and then tighten down the wing nut while holding the test tube carrier at the desired angle. With a wing nut and threaded stud securing arrangement, there is also the possibility that the test tube carrier will loosen with respect to the stationary base during a shaking procedure.
Finally, the prior art suffers from still further disadvantages with respect to the ability of the test tube rack to be quickly and rigidly secured to a shaking apparatus. In order to obtain the rigid connection between the shaking apparatus and the test tube rack in the past, tedious fastening methods have been used which do not allow the entire rack full of test tubes to be quickly removed from a shaking apparatus, refilled with test tubes and replaced or alternatively replaced by another rack filled with test tubes. Therefore, setting up tests and experiments and changing over from one test tube rack to another has generally been a time consuming process.
It would therefore be desirable to provide a test tube rack assembly which allows versatile adjustment of the angle of the test tube rack and which includes other features which allow rigid attachment of the entire assembly to a shaking apparatus yet allow quick attachment and release of the test tube rack with respect to other support portions of the assembly.